BP officials gave the procedure a 60 to 70 percent chance of plugging the leak, and Obama warned it might not work at all.

If the operation fails, engineers might not be able to stop the flow until August, when two relief wells can be drilled to intercept the oil more than a mile beneath the sea.

BP honcho Tony Hayward told NBC it could take a day or two to find out if Top Kill is working.

The procedure involves pumping mud and then cement from a ship into the gusher to seal it off, but if the force of the escaping oil is too great, the mud and cement won’t be able to stop it.

Obama is set to speak on the spill and take questions from the media today, amid accusations of bungling by BP and poor oversight by his administration — and calls to have the military take over.

Democratic consultant James Carville — normally an Obama ally — ripped the president for endangering his home state of Louisiana and blowing a political opportunity.

“The president of the United States could’ve come down here, he could’ve been involved with the families of these 11 people” who died in the oil-rig explosion, Carville said on ABC’s “Good Morning America.”

“He could be commandeering tankers and making BP bring tankers in and clean this up. They could be deploying people to the coast right now. He could be with the [Army] Corps of Engineers and the Coast Guard . . . doing something about these regulations. These people are crying, they’re begging for something down here, and it just looks like he’s not involved in this.”

Carville implored, “Man, you got to get down here and take control of this! Put somebody in charge of this thing and get this moving! We’re about to die down here!” he said.

Obama, in fact, plans to fly to Louisiana tomorrow.

“We will not rest until this well is shut, the environment is repaired and the cleanup is complete,” he said in California yesterday.

“If [Top Kill is] successful — and there are no guarantees — it should greatly reduce or eliminate the flow of oil now streaming into the Gulf from the sea floor,” Obama said, calling the spill “heartbreaking.”

Meanwhile, Obama is set to announce today that he will suspend exploratory drilling in the Artic Ocean until at least 2011.